In a known spindle of this type (see German Auslegeschrift No. 2,220,355) this cutting is effected by hand, whereupon the end of the thread, after the setting of a new bobbin, is wound around the empty bobbin and then has to be secured by means of loops or knots. In order that upon sinking of the ring bank below the bobbin foot the thread may pass over to the underwind, there are provided on its outwardly directed annular rim recesses that act like entraining grooves.
In another known spindle of the type referred to initially (see German Offenlegungsschrift No. 2,461,621) cutting edges of a substantially circular knife project from the bases of the said recesses. At the cutting edge the thread, which during underwinding has laid itself in the recesses, is cut when the bobbin is drawn upwardly from the spindle. On the substantially cylindrical sleeve part of the underwind crown there are then still located a few windings of the thread coming from the traveller. Upon movement of the ring bank over the bobbin foot there occurs -- again with the cooperation of the recesses already mentioned in the annular rim of the underwind crown -- the thread passes over the bobbin and can be wound thereon. With the above-mentioned known spindle the risk then occurs that upon acceleration of the ring bank the thread is cut by the knife in the base of the recesses, so that the thread coming from the traveller no longer winds on to the bobbins owing to the thread in the initial windings not being held. In dependently thereof the known spindle of the type above-mentioned has also the further important disadvantage that in the course of winding a bobbin the thread, a few windings of which are on the underwind crown, loosens and becomes free and can lead to damage of adjacent parts of the frame or during winding of adjacent bobbins can lead to torn threads and to considerable soiling of the frame. In particular, in cord twisting frames on which material of relative high stiffness is made release of the thread windings wound on the underwind crown occurs to a considerable extent.
The invention is based on the problem, whilst avoiding the above-mentioned disadvantages, of providing a spindle for ring spinning and ring twisting frames, especially for cord twisting frames, of the type referred to initially wherein after bobbin exchange threads coming off the underwind crown and any broken threads cannot cause any trouble in the winding of adjacent bobbins or damage to frame parts located in the vicinity. Furthermore, in an advantageous form of the invention with a spindle equipped with a disc bobbin the underwind crown of which is furnished with cutting knives, the risk of cutting the thread upon starting of the ring bank is avoided.
For the solution of the problem, in a spindle of the type referred to initially there is arranged around the cylindrical sleeve part of the underwind crown an upwardly open thread catch box the annular base of which extends outwardly from the lower end of the sleeve part, and the outer wall of which extends to the level of the upper end of the sleeve part, leaving an annular gap between itself and the annular rim. Owing to this arrangement the thread wound on the underwind crown, if it comes loose from the sleeve part after restarting of the frame does not reach adjacent frame parts or extend into the vicinity of adjacent bobbins and cause trouble. On the contrary, it is held by the catch box. The threads gathering in the catch box need to be removed therefrom only after a large number of bobbin changes. Until then, upon change of bobbin only the full bobbin needs to be removed and an empty bobbin placed on the spindle. Further work, such as cleaning torn threads from the twisting frame or repairing damage caused by these threads, is not necessary.
In development of the invention, in the case of a spindle with disc bobbins and underwind crown in which knives are provided in the recesses in the annular rim, the diameter of the lower bobbin disc is advantageously larger than the diameter on which the cutting edges of the knives are located. This has the effect that upon restarting the ring bank the thread guided upwardly from the sleeve part of the underwind crown is fed not around a knife but around the outer margin of the bobbin disc to the internal core of the bobbin, so that undesired cutting of the thread before the actual winding starts cannot occur.